The present invention relates generally to valve implants, and more particularly to artificial heart valves for repairing damaged heart valves.
A human heart has four chambers which alternately expand and contract to pump blood through the vessels of the body. The heart also includes a check valve at the upstream end of each chamber to ensure that blood flows in the correct direction through the body as the heart chambers expand and contract. These valves sometimes become damaged resulting in their inability to close when the downstream chamber contracts. When the valves do not close, blood flows backward through the valve resulting in diminished blood flow and lower blood pressure. The valves can also become damaged so they do not open sufficiently thereby resulting in diminished downstream blood flow.
Although replacement valves and surgical procedures have been developed to alleviate these conditions, they have significant drawbacks. Many earlier valves require invasive implantation techniques in which the chest is opened, the ribs are spread, the heart is paralyzed, and following cardio-pulmonary bypass, the heart is cut open to implant the valve. These invasive techniques are stressful on the patient, increase the opportunity for infection and slow recovery. As a result, valves which may be implanted with non-invasive techniques have been developed. These valves are implanted by transluminal or endothoracoscopic techniques which reduce many of the drawbacks associated with invasive surgery. However, many of these valves also require the damaged native heart valve be removed prior to implanting the artificial valve. Removing the native valve increases the risk that a portion of the valve will migrate through the body and block vessels downstream from the heart.
Many mechanical and bioprosthetic valves have been developed to replace native heart valves. See C. A. Hufnagel, Basic Concepts in the Development of Cardiovascular Prostheses, 137 Am. J. of Surg. at 285-300 (1972). See also D. E. Harken et al., Partial and Complete Prosthesis in Aortic Insufficiency, 40 J. Thorac and Cdvsc Surg., no. 6., at 744-62 (1960). These valves include ball-valve prostheses, flap-valve prostheses, polymeric trileaflet synthetic valves, and bioprosthetic valves made from animal allograft tissues such as pig valves and preserved heterologous bovine and porcine pericardial tissue valves. See H. B. Lo et al., A Tricuspid Polyurethane Heart Valve as an Alternative to Mechanical Prostheses or Bioprostheses, 34 Trans. Am. Soc. of Art. Int. Organs at 839-44 (1988); and S. L. Hilbert et al., Evaluation of Explanted Polyurethane Trileaflet Cardiac Valve Prostheses, 94 J. Thorac and Cdvsc Surg. at 419-29 (1987). Most of the aforementioned valves require open chest surgery and cardio-pulmonary bypass for implantation.
More recently percutaneous and transluminal implantation have been suggested. See Steven R. Bailey, Percutaneous Expandable Prosthetic Valves Textbook of Interventional Cardiology, chap. 75 (1995) (referencing work of Andersen et al.) See also Knudsen et al., Catheter-implanted Prosthetic Heart Valves, 6 Int""l J. of Art. Organs, no. 5, at 253-62 (1993); Knudsen et al. Transluminal Implantation of Artificial Heart Valves. Description of New Expandable Aortic Valve and Initial Results With Implantation by Catheter Technique in Closed Chest Pigs, 13 European Heart J. at 704-08 (1992); and U.S. Pat. No. 5,411,552 (Andersen). The Andersen device includes a heterologous pig valve mounted in an annular ring. Due to the size of this device, it must be implanted by direct abdominal aortic incision and entry. Further, the Andersen device requires a separate inflating balloon for its deployment. U.S. Pat. No. 5,397,351 (Pavcnik) describes an expandable caged poppet for percutaeuous implantation in an aortic valve site. However, the size of the Pavcnik device makes percutaneous implantation difficult. U.S. Pat. No. 5,885,601 (Bessler) describes a transluminal valve implantation but does not describe the specific valve construction. The Bessler procedure includes excision, vacuum removal of the native valve, cardio-pulmonary bypass and backflushing of the coronary arterial tree.
Among the several objects and features of the present invention may be noted the provision of an artificial heart valve which accommodates implantation without removing the damaged native heart valve; the provision of a valve which may be implanted using non-invasive surgery; the provision of a valve which permits implantation without the need for cardio-pulmonary bypass; and the provision of a valve which permits implantation by conventional open chest surgery and cardio-pulmonary bypass.
Briefly, apparatus of this invention is an artificial valve for repairing a damaged heart valve having a plurality of cusps separating an upstream region from a downstream region. The artificial valve comprises a flexibly resilient frame sized and shaped for insertion in a position between the upstream region and the downstream region. The frame has a plurality of peripheral anchors for anchoring the frame in the position between the upstream region and the downstream region and a central portion located between the anchors. In addition, the artificial valve includes a flexible valve element attached to the frame and to the central portion of the frame. The valve element has an upstream side facing the upstream region when the frame is anchored in the position between the upstream region and the downstream region and a downstream side opposite the upstream side facing the downstream region when the frame is anchored in the position between the upstream region and the downstream region. The valve element moves in response to a difference between fluid pressure in the upstream region and fluid pressure in the downstream region between an open position in which the element permits downstream flow between the upstream region and the downstream region and a closed position in which the element blocks flow reversal from the downstream region to the upstream region. The valve element moves to the open position when fluid pressure in the upstream region is greater than fluid pressure in the downstream region to permit downstream flow from the upstream region to the downstream region, and the valve element moves to the closed position when fluid pressure in the downstream region is greater than fluid pressure in the upstream region to prevent flow reversal from the downstream region to the upstream region.
In another aspect of the invention, the artificial valve comprises a flexibly resilient frame and a flexible valve element attached to the frame. The valve element has a convex upstream side facing the upstream region when the frame is anchored in the position between the upstream region and the downstream region and a concave downstream side opposite the upstream side facing the downstream region when the frame is anchored in the position between the upstream region and the downstream region. The valve element moves in response to a difference between fluid pressure in the upstream region and the downstream region between an open position and a closed position.
In yet another aspect of the present invention, the artificial valve comprises a plurality of U-shaped frame elements sized and shaped for insertion in the heart in the position between the upstream region and the downstream region. Each of the plurality of frame elements has opposite ends. The elements are joined together generally midway between their respective ends at a junction of the elements. In addition, the artificial valve includes a band extending between each frame element and an adjacent frame element to limit spacing between the frame elements. Further, the artificial valve includes a flexible valve element attached to the junction of the frame elements. The valve element has a convex upstream side facing the upstream region when the frame elements are inserted in the position between the upstream region and the downstream region and a concave downstream side opposite the upstream side facing the downstream region when the frame elements are inserted in the position between the upstream region and the downstream region. The valve element moves in response to a difference between fluid pressure in the upstream region and fluid pressure in the downstream region between an open position and a closed position.
In still another aspect, the invention includes the artificial valves described above having a frame which is collapsible to a configuration having a maximum width less than about 18 mm in combination with an instrument for inserting the artificial valve in the position between the upstream region and the downstream region. The instrument includes a holder having a hollow interior sized for holding the artificial valve when the frame is in the collapsed configuration. In addition, the instrument includes an elongate manipulator attached to the holder for manipulating the holder into position between the upstream region and the downstream region and an ejector mounted in the hollow interior of the holder for ejecting the artificial heart valve from the hollow interior of the holder into position between the upstream region and the downstream region.
Still further, the invention includes an endothoracoscopic method of inserting an artificial valve between a plurality of cusps of a damaged heart valve. The method comprises the steps of making an opening in a chest wall, making an incision in a heart and inserting an end of an elongate instrument through the opening made in the chest wall and incision made in the heart. In addition, the method includes positioning the inserted end of the instrument adjacent the cusps of the damaged heart valve and ejecting an artificial valve from the end of the instrument into a position between the cusps of the damaged heart valve without removing the damaged heart valve from the heart.
Moreover, the invention includes a transluminal method of inserting an artificial valve between a plurality of cusps of a damaged heart valve comprising the steps of making an incision in a vessel leading to the heart and inserting an end of an elongate flexible instrument through the incision made in the vessel. In addition, the method includes pushing the end of the instrument through the vessel until the end is adjacent the cusps of the damaged heart valve and ejecting an artificial valve from the end of the instrument into a position between the cusps of the damaged heart valve without removing the damaged heart valve from the heart.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.